OK it does sound as though you might be affected by the old win7-64bit problem still. I will admit to never seeing this problem myself when I have flashed my phone, I think I know why but can't say here

You said in your PM that you ran the USB fix but that still did not help. Can I ask if you have rebooted your PC since running the libs?

Another thing to try would be to try and flash with another USB cable / Port or a completely different PC?

One other popular scenario would be to use an Ubuntu Live CD as this would load the generic USB drivers as it boots in to the OS. The commands are almost the same too, almost.

Hope this helps?